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Thread: Using Muriatic Acid to Safely Lower Your Pool's pH

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    Default Using Muriatic Acid to Safely Lower Your Pool's pH


    Using Muriatic Acid Safely:

    Product Description
    20 degree Baume' 31.45% Muriatic Acid AKA hydrochloric acid AKA "MA"
    Avoid diluted (15%) or low-fume acid, since they often contain OTHER chemicals that may mess up your pool! Of course, if you are 100% sure the only ADDED chemical is water, 15% acid is fine.
    MSDS - Material Safety Data Sheets for muriatic acid
    Hasa Pool
    Sunnyside Corp
    Crown Muriatic Acid at Lowe's
    TransChem Muriatic Acid at some Ace Hardware stores
    Other sources: Any hardware, building supply, or home care store is a possible source. Brands may vary, even within a single chain.

    Dewalt Safety Glasses (Amazon)
    Large black nitrile gloves(Amazon)
    Step by step:

    Video demonstration of these steps:
    This is the preliminary unedited video, without voice-over and graphics, but it completely demonstrates the correct method.

    # 1 - Make sure your pool pump is on, and leave it on for at least 1 hour after you add acid.

    # 2 - Get a sharp stainless kitchen paring knife, plastic gloves and some sort of glasses BEFORE opening the bottle. Put on the gloves and glasses.

    # 3 - Splash some water on the pool deck, place the bottle in the puddle on the deck, and remove the lid.

    # 4 - Either gently pull the seal from the bottle OR use the knife to cut it away. If you use the knife, immediately rinse the blade in the pool.

    # 5 - Once the lid is off, and the seal removed, take the bottle and submerge it partially in the pool.

    # 6 - Pour the acid into the pool by tilting the bottle. Keep the mouth of the bottle only a couple of inches above the pool's surface.

    # 7 - Your basic dose is 1/4 of a 1 gallon bottle per 10,000 gallons of pool water. Do NOT try to measure this! Under-guesstimate the dose, and add more later if needed. (Pouring acid from one container to another will release a LOT of noxious fumes!)

    # 8 - Cap the bottle tightly.

    # 9 - Store the bottle outside in an opaque plastic container. If you do store the acid indoors, be sure to put inside a sealed heavy duty garbage bag. Read the explanation, below.

    #10 - Rinse any spills off you or the deck promptly with pool water. If you should splatter the acid in your eyes, let go of the bottle and IMMEDIATELY roll over into the pool. Open your eyes underwater, and swim away from the area where you have added acid. This will flush your eyes completely and safely. (If you can't swim, move a few feet away from your work area, lay on the deck and submerge your head in the pool. Force your eyes open in the water.)

    #11 - Never, NEVER use a hose with a nozzle to rinse your eyes -- a high pressure stream of water can also do immediate, serious damage to your eye. If for some reason, you cannot put your face in the water, move a hose with NO NOZZLE next to you BEFORE you begin adding acid. Turn on the water so that it flows gently out of the hose, and LEAVE IT RUNNING till you have re-sealed and rinsed the bottle of acid. If you should have a problem, use the hose to flush your eyes.

    Any acid can be used to lower your pool's pH or alkalinity, but some are better than others. Organic acids, like ascorbic acid (Vitamin C) or citric acid (lemon juice) are used to remove stains -- but they are destroyed by chlorine and are expensive. The most common 'pool acids' ("pH Minus", "pH Down", etc.) are based on sodium bisulfate, a partially neutralized form of sulfuric acid. However, sulfates increase concrete corrosion, and sodium bisulfate is expensive, compared to muriatic acid.

    We usually recommend hydrochloric acid, called "muriatic acid" when sold for commercial purposes, for use instead except on very small pools. There are several reasons:
    + it is cheaper than sodium bisulfate.
    + it does not add sulfates, which are damaging to inground concrete pools.
    + it does add chlorides, which are desirable in pools with SWCG.

    But muriatic acid is not perfect.

    It is perfectly safe for you and your pool, once it's diluted. But until then, because it is so strong, it can be VERY damaging. Like several pool chemicals (including bleach, powdered forms of chlorine, and sodium bisulfate) it can cause permanent eye damage almost instantly. It will discolor or damage almost anything you get it on, and will burn your skin quickly. So, you have to be very careful how you handle it. Fortunately, it's not hard to handle it correctly -- just follow the directions above!

    It has one unique hazard, however.

    Unlike most other common acids, hydrochloric acid is actually a gas in its pure form (HCl). For use, it's dissolved in water. But, at the concentration sold and labeled muriatic acid (~31%) the gas -- HCl -- will try to leave the water. This gas is painful to breath, and can be dangerous. It is EXTREMELY damaging to copper wiring or bare metal. If you follow the handling instructions above, you'll avoid breathing the fumes. But you MUST also be very careful how you store the acid, once you've unsealed the bottle. You must NOT store the acid in your garage or pump room, simply with the cap on. Enough fumes will often leak out to damage nearby metal or wiring. If at all possible, store it outside in a small covered plastic garbage can.
    If you must store muriatic acid inside do this:
    # 1 - After use, cap the bottle tightly.
    # 2 - Rinse the entire bottle off in the pool.
    # 3 - Place the bottle inside a heavy duty garbage bag, and then seal the bag with a twist tie.
    # 4 - You may then store the bottle inside.
    # 5 - When you next use the bottle, carry the bag and bottle outside BEFORE opening the bag. That way, any fumes that have accumulated can dissipate harmlessly.

    Last edited by PoolDoc; 05-30-2018 at 07:28 PM.

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